A scanning probe microscope is configured to measure the surface shape of a sample by causing a probe attached to the front end of a cantilever to approach or come into contact with a sample surface. As measurement modes of the scanning probe microscope, there have been known (1) a contact mode in which the surface shape of the sample is measured while maintaining an inter-atomic force between the probe and the sample to be constant, (2) a method (hereinafter, appropriately referred to as a “dynamic force mode (DFM measurement mode)”) in which the shape of the sample is measured by using the fact that the amplitude of the probe is attenuated due to intermittent contact between the probe and the sample when the probe approaches the sample by forcibly vibrating the cantilever near a resonance frequency by using a piezoelectric element, and (3) a method (hereinafter, appropriately referred to as a “non-contact mode (NC-AFM measurement mode)”) in which the shape and property of the sample are measured using the fact that a resonance state of the probe is changed by a force acting between the probe and the sample when the probe approaches the sample by forcibly vibrating the cantilever near the resonance frequency by using the piezoelectric element.
The scanning probe microscope includes a fine movement unit that includes two (two-axis) fine movement mechanisms (piezoelectric elements) that respectively scan the sample in an xy (plane) direction and one (one-axis) fine movement mechanism (piezoelectric element) that scans the sample in a z (height) direction. For example, the sample is mounted on the surface of a stage disposed on the fine movement unit. Since a voltage applied to the piezoelectric element is proportional to the displacement of the piezoelectric element to some extent, height information related to the sample surface may be calculated from the voltage applied to the piezoelectric element. However, since the operational characteristics of the piezoelectric element are hysteresis or creep, it is difficult to obtain an accurate position of the piezoelectric element from the applied voltage.
Thus, a technology in which position detecting sensors using impedance are provided on the piezoelectric elements has been developed (JP-A-2009-225654). By using such a technology, it is possible to respectively detect the positions of the three (three-axis) piezoelectric elements of the fine movement unit, and it is possible to calculate a three-dimensional position of the sample disposed on the fine movement unit.